Researchers from
MIT have unearthed high concentrations of lead in the Indian Ocean, as well as
areas closer to population centers such as Singapore.
Leaded gasoline has been slowly phased out worldwide
since the 1970s, when studies proved that apart from degrading vehicles’
catalytic converters, it was also capable of neurological and cardiovascular
damage.
Today, 185 countries have stopped using leaded gasoline;
six others, including Afghanistan, Iraq and North Korea, plan to phase it out
in the next two years. But while leaded gasoline usage has decreased
drastically in the last few decades, lead is still pervasive in the
environment.
In this study, the researchers analyzed water and coral
samples from the Indian Ocean, tracing the history of anthropogenic lead over
the last 50 years.
In analyzing their samples, they found an oddity: In
samples taken off the coast of Singapore, they found a type of lead they did
not expect in this region of the world.
Most countries around the Indian Ocean used leaded
gasoline produced in Europe and the Middle East.
The lead found near Singapore, however, matches the kind
once used in North American gasoline.
“It’s almost as if Singapore had gone off and imported a
whole lot of lead from the United States. It doesn’t make any sense why they
would do that, because there are more local sources that presumably would be
cheaper, more economical,” said Professor Ed Boyle of MIT’s Department of
Earth, Atmospheric and Planetary Sciences.
Hopeful in finding the source of the anomalous lead,
Boyle and his students began collecting water and coral samples from the Indian
Ocean three years ago. The team obtained samples from various sources: Corals
from the middle of the Indian Ocean came from a Japanese-funded expedition, while
samples from the Singapore shores were collected by the MIT team.
Once the researchers brought the samples back to the lab,
they started analyzing corals for trace amounts of lead, determining the type
of lead in each sample. By ascertaining how much lead was deposited in a given
year, the researchers were able to reconstruct a history of lead in the Indian
Ocean for the past 50 years.
They found that lead levels began to increase in the
mid-1970s, peaking in 2002 and 2003 before beginning to decline — a timeline
consistent with the region’s pattern of industrialization and leaded gasoline
use.
“It is an indication of the human footprint on the planet
that essentially all the lead in the oceans now is from human activities. It’s
very hard to find a trace of the lead that’s there naturally,” said Boyle.
The group also found that lead concentrations in the
Indian Ocean are now higher than in the northern Atlantic and northern Pacific
oceans.
“One explanation may be that Asian and African countries
lagged North America and Europe both in industrialization and then in phasing
out leaded gasoline. As a result, the Indian Ocean has had less time than the
Atlantic and Pacific to dissipate lead pollution,” he explained.
Boyle added that the levels of lead observed,
particularly in the open ocean, pose no environmental concern as yet. Just as
did the Atlantic Ocean — in which he has observed a steady decrease in lead
over the years — he anticipates the Indian Ocean’s natural recovery.
“It’s a demonstration of the ability of the ocean to
clean itself when we clean up our act and stop polluting it,” he said.
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Source: MIT
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